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My iPhone 12 is not transmitting sound during calls.
The I2S2_AP_TO_BB_DOUT line is the digital audio data output line between the Application Processor (AP) and the Baseband (BB) processor on our device.
I2S (Inter-IC Sound): This is the serial communication protocol used for digital audio transmission.
AP (Application Processor): Android/iOS operating system, applications and audio processing run here.
BB (Baseband Processor): Responsible for cellular communication (calls, SMS, data) and the transmission of conversation audio.
DOUT (Data Out): Indicates the output direction of digital audio data.
The digital audio data processed from the microphone is transmitted from the AP to the BB via this line. The Baseband processor then sends this sound to the other party over the network.
Problem – No Sound Reaching the Other Party
When the device arrived, there was no sound reaching the other party during calls. In these types of malfunctions:
The microphone may be working.
The audio codec integrated circuit may be functioning.
However, if there is a break, attenuation, or short circuit in the I2S2_AP_TO_BB_DOUT line, the digital audio cannot reach the BB.
As a result:
The user can hear the other party.
The other party cannot hear the user.
This directly points to a TX (audio transmission) problem originating from the I2S data line.
The I2S2_AP_TO_BB_DOUT line is the digital audio data output line between the Application Processor (AP) and the Baseband (BB) processor on our device.
I2S (Inter-IC Sound): This is the serial communication protocol used for digital audio transmission.
AP (Application Processor): Android/iOS operating system, applications and audio processing run here.
BB (Baseband Processor): Responsible for cellular communication (calls, SMS, data) and the transmission of conversation audio.
DOUT (Data Out): Indicates the output direction of digital audio data.
The digital audio data processed from the microphone is transmitted from the AP to the BB via this line. The Baseband processor then sends this sound to the other party over the network.
Problem – No Sound Reaching the Other Party
When the device arrived, there was no sound reaching the other party during calls. In these types of malfunctions:
The microphone may be working.
The audio codec integrated circuit may be functioning.
However, if there is a break, attenuation, or short circuit in the I2S2_AP_TO_BB_DOUT line, the digital audio cannot reach the BB.
As a result:
The user can hear the other party.
The other party cannot hear the user.
This directly points to a TX (audio transmission) problem originating from the I2S data line.
